The steep drop in equities that wiped out all of the gains for the year coincided with President Obama’s 50th birthday. At a celebration in Chicago on Wednesday night, the president said he is still learning about details of the recession that rocked his administration in the first year.

“We just found out a week ago that the economy the last few months in 2008 was even worse than we had realized,” Mr. Obama told supporters at a fundraiser. “I mean, the economy had contracted by 8 percent. It was the worst economy we had ever seen.”

He cautioned that he needs more time to fulfill his campaign promise of economic prosperity.

“When I said, ‘change we can believe in,’ I didn’t say “change we can believe in tomorrow,” Mr. Obama said to laughter. “Not ‘change we can believe in next week.’ We knew that these challenges weren’t made overnight, and they weren’t going to be solved overnight.”

Republicans say Mr. Obama’s team is still erecting barriers to job creation. In July, the administration moved forward with a number of regulations: 379 final rules, 229 proposed regulations and 10 “economically significant” rules, with a total estimated cost to businesses of more than $9.5 billion.

“When the American people think the economy is ‘fragile,’ ‘vulnerable,’ ‘weak’ and ‘uncertain,’ the Obama administration should cut red tape,” said Sen. John Barrasso, Wyoming Republican and vice chairman of the Senate Republican Conference.

The White House in recent months has been touting its efforts to streamline regulations and eliminate unnecessary rules, in response to a sustained outcry from business leaders.

The president and his economic advisers had said the debt deal signed into law Tuesday was needed to calm financial markets. As the Dow Jones industrial average sank on its way to a loss of more than 500 points Thursday, Mr. Carney said, the cause was more likely tied to economic worries about Europe.

“Markets go up and down,” Mr. Carney said. “Our view of this is, while the agreement … did not achieve the kind of supersized deficit reduction that we sought, it did end the uncertainty” about the potential of the government defaulting on its obligations.

The White House spokesman also turned away speculation that Treasury Secretary Timothy F. Geithner might be leaving his post soon.

“He hasn’t decided when he will leave,” Mr. Carney said. “He has said he will be here for the foreseeable future. That’s what he tells us.”

Mr. Obama plans a bus trip through Midwestern swing states Aug. 15-17 to talk about jobs. Reporters pressed Mr. Carney to explain why the public should think the president can be effective, given his economic record.

“He will continue to make the case that we need to take the measures necessary as a country, working together with Congress, that will spur greater economic growth and create more jobs,” Mr. Carney said. “He is working very closely with his senior economic advisers to come up with new proposals to help advance growth and job creation.”

After the markets closed on the disastrous trading day, Mr. Obama gathered with family and friends at the White House for a birthday dinner. In an email to supporters earlier, first lady Michelle Obama said her husband is “earning every last one of those gray hairs.”